Tunnel expert, MarcoPradera, project lead at Siemens shares his experiences from working underground at Switzerland’s most fascinating construction site… the Gotthard Base Tunnel (GBT) which is the centerpiece of the new transalpine railway link in and through Switzerland. GBT runs for an impressive 57 kilometers from thenorth portal in Erstfeld, Canton Uri, south to Bodio, Canton Tessin. To create the two single-track main tubes and the safety, ventilation and cross tunnels, 28.2 million tons of rock have been removed since the first blast 17 years ago.

It goes without saying that safety is paramount in a tunnel where in the near future more than 200 trains a day will barrel through the tubes at speeds up to 250 km/h. The tubes are connected every 300 meters by crosscuts that allow train passengers to escape to the other tube in case of a fire. “The biggest danger isn’t fire, it’s suffocation,” explains Pradera.

Fire detectors in cages

Fire detection in the four emergency-stop stations is handled by three different detection systems, which control the air dampers directly if an evacuation becomes necessary. The controllers check and record the monitoring data every few milliseconds to ensure the history can be traced and the trigger parameters optimised. The installation of the Fibrolaser fire detection technology from Siemens required special modifications.

Typically, Fibrolaser cables are mounted at a distance of 5 cm from the wall because this ensures optimal transmission of temperature readings. For technical reasons, however, they were mounted directly against the concrete wall in the GBT. In addition, Fibrolaser sensors on the floor watch for initial signs of danger. “A stuck wheel on the train, for example, or leaking fluid can catch fire,” adds Pradera.

In addition to Fibrolaser, the Gotthard Base Tunnel is equipped with thermal imaging cameras and smoke detectors which continuously measure the temperature and check the air for smoke particles. To protect them against the harsh environmental conditions in the tunnel, they were enclosed in cages – another custom design for the GBT.

No access without a stress EKG

Working in the tunnel is anything but child’s play. Each person has to pass a heat test and stress EKG required by the Swiss Accident Insurance Agency (SUVA), followed by safety training: People without training are not permitted access. Only those who pass the test are allowed on site. At all times, they are required to wear reflective safety clothing, a helmet, heavy-duty mountain boots and a heavy backpack that weighs 15 kg and contains life-saving gear.

When regular rail service begins in December 2016 after thousands of test runs, BT’s Gotthard Base Tunnel expert will finally be able to take it a bit easier. Asked whether he plans on ever taking a train through the tunnel, Pradera says: “Never say never. But if I have a choice, I prefer to go over the mountain instead of through it. Not for safety reasons, but simply because you see a lot more.”

Siemens